Atrial fibrillation is a common sustained cardiac arrhythmia and a major cause of stroke. Atrial fibrillation results in a fast and irregular cardiac rhythm which often leads to palpitations and a deterioration of cardiac function with cardiac output decreasing by an average of 30%. There is also an increased incidence of intra cardiac thrombosis (blood clotting) which can potentially lead to embolic events such as strokes. Consequently, 20 to 35% of cerebrovascular accidents (CVAs) are related to paroxysmal or chronic atrial fibrillation.
This condition is perpetuated by reentrant wavelets propagating in an abnormal atrial-tissue substrate. Various approaches have been developed to interrupt wavelets, including surgical or catheter-mediated atriotomy. Atrial fibrillations can also be treated by pulmonary vein isolation which proves to be insufficient in 30 to 50% of paroxysmal atrial fibrillation patients and 90% of permanent atrial fibrillation. In such cases, it may be necessary to ablate and perform linear lesions in addition to pulmonary vein isolation, in the right and left atriums. These linear lesions have been done using RF ablation catheters for about a decade. Each lesion should ideally be transmural and continued with adjacent lesions so as to obtain a final linear lesion blocking electrical activity between two natural areas of block. The most common locations of these lines are the mitral isthmus in the left atrium, with a lesion extending from the mitral annulus to the left inferior pulmonary vein. Other possible locations include the roof of the left atrium, with a lesion connecting the ostium of the superior right pulmonary vein to the left superior vein. However, because conventional catheters generally treat tissue in a localized manner, numerous repeated applications of the catheter are typically needed to form a linear lesion. Thus, while the formation of linear lesions is possible, it can be a time-consuming, labor-intensive procedure.
Prior to treating the condition, one has to first determine the location of the wavelets. Various techniques have been proposed for making such a determination. None of the proposed techniques, however, provide sufficient assistance in guiding the formation of the linear lesion or easing the linear line assessment process, particularly for regions of the mistral isthmus and the left atrium roof.